Hello dear JMH,
I have another issue regards to my 2D modelling. I have experimental results for that embankment when I want to do numerical simulation. In the experimental work, the flow is reaches to the crest where I have a pilot channel which is shown in figure 1 much much faster that numerical one. I changed the friction value of the channel bed, didn't make big difference. Here I will post the cas file and hope you will figure out the reason.